Radermachol and naphthoquinone derivatives from Tecomella undulata: Complete ¹H and ¹³C NMR assignments of radermachol with the aid of computational ¹³C shift prediction

1865-1870Petroleum ether extract of the heartwood of Tecomella undulata affords radermachol, an unusual rare pigment and 2-isopropenylnaphtho[2,3-b]furan-4,9-quinone along with lapachol, tecomaquinone-I, dehydro-α-lapachone, α-lapachone, β-lapachone, cluytyl ferulate, stigmasterol and β-sitosterol. Radermachol and 2-isopropenylnaphtho [2,3-b]furan-4,9-quinone are being reported for the first time from genus Tecomella. Complete assignments of ¹H and ¹³C NMR signals of polyketide, radermachol 1, have been achieved by the ¹³C NMR chemical shift prediction using ab initio MO and DFT/GIAO methods in addition to 2D-NMR techniques

Aromatic Polyketide Production in <i>Cordyceps indigotica</i>, an Entomopathogenic Fungus, Induced by Exposure to a Histone Deacetylase Inhibitor

Cultivation of <i>Cordyceps indigotica</i>, an entomopathogenic fungus, in the presence of suberoyl bis-hydroxamic acid (an HDAC inhibitor) greatly activated its polyketide synthesis apparatus to afford six novel aromatic polyketides, indigotides C–F (<b>1</b>–<b>4</b>), 13-hydroxyindigotide A (<b>5</b>), and 8-<i>O</i>-methylindigotide B (<b>6</b>). The structures of these compounds were determined by NMR spectroscopic analyses. Among the compounds, indigotides C–E (<b>1</b>–<b>3</b>) possessed unprecedented dimeric polyketide frameworks possibly generated via a [4 + 2] cycloaddition or Michael type reaction

Structures and Biomimetic Synthesis of Novel α‑Pyrone Polyketides of an Endophytic <i>Penicillium</i> sp. in <i>Catharanthus roseus</i>

Novel polyketides, citreoviripyrone A (<b>1</b>) and B (<b>2</b>), known citreomontanin (<b>3</b>), and (−)-citreoviridin (<b>4</b>) were isolated from the mycelium of the endophytic fungus. The endophytic fungus, which belongs to the genus <i>Penicillium</i>, was separated from surface-sterilized healthy leaves of <i>Catharanthus roseus</i>. The structures of <b>1</b> and <b>2</b> were determined on the basis of NMR data, and <b>1</b> was characterized as an α-pyrone polyketide featuring bicyclo[4.2.0]octadiene. The biomimetic synthesis of <b>1</b> and <b>2</b> from <b>3</b> elucidated a plausible biosynthetic pathway. Both Zn(II)-type and NAD⁺-dependent histone deacetylase inhibitors significantly enhanced the production of <b>1</b> and <b>3</b>